Magnetic rotoric brake system for electric induction motors



Nov. 29, 1949 E. J. BRoussousE MAGNETIC ROTORIC BRAKE SYSTEM FOR ELECTRIC INDUCTION MOTORS v Filed May 20, 1946 Patented Nov. 29, 1949 MAGNETIC ROTORIC BRAKE SYSTEM FOR ELECTRIC INDUCTION MOTORS Edouard Jean Broussouse, Angouleme, France Application May 20, 1946, Serial No. 670,895 In France September 17, 1945 2 Claims.

This invention relates to a magnetic rotoric brake system for electric induction motors comprising a brake with a fixed magnetic ring and an armature plate rendered fast with the rotating parts of the motor by a driving assembly with an axially sliding movement.'

Such braking devices which have already been proposed generally oier the following disadvantages:

When the braking ceasesand on starting the motor, the axially sliding movement which is necessary for releasing the armature plate from the brake ring is generally effected by means of aresilient member such as an antagonistic spring. Furthermore said spring must be strong enough for also insuring the stability of the armature plate during the operation of the motor, i. e. for avoiding a rattling capable of causing detrimental interfering frictions and possibly a prejudicial wear and tear. It is thus necessary to increase the attractive force, which determines the braking, of the antagonistic thrust of said spring.

On the other hand, the axial thrust of a spring or any other resilient member against a plate rarely operates in a well distributed manner on the periphery of the plate and this often results in jammings in the sliding joint.

Finally, owing to the presence of the resilient antagonistic member in brakes of this kind the sliding joint is located in a place adjacent to the ends of the motor shaft, which causes a certain friction caused by the tangential stress occurring at the place of said sliding joint at the moment when the brake is applied.

It is also well known to apply the brake by a resilient member such as a spring, and to release the same under the inuence of the rotoric field. But in such case, the rotor is braked while stopped, and hence such devices are objectionable for certain uses, such as for motors of machinetools.

The braking system according to the invention which obviates said drawbacks is characterized by a mechanical arrangement of the armature plate according to which a part of said plate which is magnetically permeable is placed in one of the circular magnetic elds provided at each end of the rotor by the rotoric currents which pass through the leads for the connection of the active bars or bundles and so that the action `of said eld insures, during the normal operation of the motor, both the releasing of the contact of the armature plate from the brake ring and a good stability of said plate during the rotation.

Furthermore, the driving member for the actuation of the sliding armature plate by the rotor will be established with advantage towards the periphery of the rotor in order to reduce as much as possible the friction caused when the brake isV applied.

A form of execution of the device using the system according to the invention is shown by way of example in the appended drawing, in which:

Fig. l is a sectional view through a whole arrangement by which the invention is applied, for example, to one end of the rotor of a so called short-circuit or squirrel-cage motor.

Fig. 2 is a sectional view through a part of Fig. l in which the armature-plate is especially shown in the motor braking position, and

Fig. 3 is a sectional view showing the same part oi Fig. 1 in which the armature-plate is especially shown in the position for the normal operation of the motor.

In the drawing:

The short-circuit motor 4 has a rotor 5 which comprises a squirrel-cage with active bars such as 6 passing through the laminations 'I and connected at their ends by two end rings such as 8. The end bell 8 of the motor 4 supports a magnetic ring It containing an energizing coil II supplied with current by the leads I2 in any suitable manner. The outer diameter of said ring I0 can correspond, for example, to that of the conductor ring 8 forming the end of said cage. Furthermore, the ring I0 can comprise two circles or pole pieces I 8, I9 connected therewith by a rigid anchorage, not shown.

A magnetically permeable armature-plate I3 having two planed faces IB-I'I is connected with the rotor 5 by a series of spindles such as I4 penetrating into the ring 8 through suitable holes I5 which allow a certain sliding movement along the axis of the motor of said plate I3 which, owing to this fact, can come to bear alternately upon the planed faces 2B or 2I-22 pertaining to the cage ring 8 and to the poles I8, I9 of ring II.'I respectively.

The well known operation of the magnetic brake is effected as shown in Fig. 2 in which the eld of lines of force is to be seen which is closed by the plate I3 and determines the adherence of the faces 2I-22 with face I'I.

When the braking ceases through an interruption of the current in the coil II and when the motor is started the ring 8 becomes the seat, by sectors, of alternating currents the direction of which changes with the rotoric periodicity but sliding movement towards the ring 8 and then i.

to insure its stability during the operation by maintaining the contact between the faces IB and 20.

This double result is obtained with a great simplicity without the use 'of any antagonistic springs which reduce the effectiveness of the brake or of any auxiliary member, controlled or not controlled. Furthermore, the construction is very compact and requires particularly little space.

."It vhas beenshownin Fig. 1 that the pins I4 rest in` driving relation in holes I5 provided in thering 8. bestrengthened yby .causing the pins to enter `the rotor body wholly or partly with any suitable .If necessary, said connection can diameter but preferably with as large a diameter Moreover,.the sliding coupling by outer. coupling withlany suitable modifications.

What I claim is:

lp In an electric motor having a shaft and a l rotor keyed on the shaft, a braking device comprising magnetic means xedly positioned adj acent one end of the rotor, a plate intermediate the `magnetic means andthe rotor, means coupling the 4'plateto thefshaft whereby the plate is rotatable with but freely shiftable axially of the shaft, means comprising a friction surface fixed to the magneticmeansin cooperating relationship with the plate, and magnetically permeable elements fixed to the plate and located within the rotoric eld developed by the rotor, whereby the plate is retracted from braking position by energizetion of the rotor and is thereby prevented from rattling during non-braking operation of the motor.

.2. AIn lan electric motor having a shaft and a rotor keyed to the shaft and including an end ring concentric with the shaft and having a plane annular face remote from the rotor, a braking device comprising magnetic means iixedly positioned4 adjacent but spaced from said end ring, a plate intermediatethe magnetic means and the end ring and slidably mounted on the ring, fixed f means comprising a friction surface in cooperati ing .relationship with the plate and located on the same side thereof as the magnetic means, the "plate having plane surfaces adapted to cooperate selectively with said end ring face and saidffrictionwsurface, .at least part of the plate being of magnetically permeable material whereenerg-ization of. the'motor causes the plate to .be attracted .tothe rotoiyand means to energize the magneticrmeans thereby to attract the plate into cooperation with the friction surface for producing a braking torque on the rotor.

a. EDOUARD 'JEAN BROUSSOUSE.

l vREFERENCES CITED The followingreferences are of record in the file of' this patent:

UNITED STATES PATENTS Number Name Date I 832;'713 `Wiard Oct. 9, 1996 `1,508,100 Hawley Sept. 9, 1924 FOREIGN PATENTS Number Country Date 1,214,981 l:Switzerland Aug. 16, 1941 

